Directive microwave radio antenna



G. c. SOUTHWORTH DIRECTIVE MICROWAVE RADIO ANTENNA Original Filed Nov. 28, 1941 Feb. 1, 1949.

3 Sheets-Sheet 1 FIG. 2

lNl/ENTOR G. C. SOUTHWORTH 71 b1 @ZTORNEV G. c. souTHwoRTH DIRECTIVE MICROWAVE RADIO ANTENNA Feb. 1, 1949..

3 Sheets-Sheet 2 Original Filed Nov. 28, l94l- Fla. 9

I M/l/E/VTOR a. c. sour/ wo TH A 7T RNEY Feb. 1, 1949.. s. c. SOUTHWORTH 2,460,401

v DIRECTIVE MICROWAVE RADIO ANTENNA Original Filed Nov. 28, 1941 3 Sheets-Sheet 3 lNVENTOR G. C. SOUTHWORTH A7 ORNEI/ l 'atented Feb. 1,, 1949 2,469,401 ""DIEE T V T I E YEJBADIQA FEEN George C Southworth, Red Bank, N. J.,.-ass ignor to Bell Telephone Laboratories, Inqorpoi'ated,

" s New York, 'N. Y.,' a co ,c 1 s. This invention relates to the transmission of ultrahigh frequency...electromagnetic waves and .amorer particularly to apparatus systems and methods adapted for; the la'unching of radio .waves int'o jspace .and for the. reception of such waves. SThe present application isa division of my appli- Iceman. Serial No...420,747,.fi1ec1 November 23,1941

(United States Patent .No. 2;40. 5,242; granted: Aug'ust 6;. 1946) ,,.the.disc1 osure of which is to be deemed incorporated I herein.

The invention has as its principal object the Y provisionof newandirnproved means. for. the directive-radiation and reception of radio waves, j and.more-e sp ec ially. antennas adaptedfor the-rafl di o .bearn transmission of microwaves. EOne of the objects is ,to satisf yitheneedfo r an .jantenna, or unity antenna fora nulti'mlit array, that is fairly-smalLgenerally elongated all-(1.81811- .der, and directive. principallyalong its axis, i that is, in the; direction in; which it s pointed. An j agnt iine f this kind would be especially .vvell "adapted fornany applications where ,space, shape and weight are significant factors, as for typicalexample in an arrayor in connection with v olojec t locators. or'firadarsf; for installation on Y-airciaft.

In an embodiment ofnthefl-invention to leede- .s ibed indetailhereinafter, an ;elo ngated.slender an'tenna or, antenna '.unit;with: the; desired ;-endon? or "end-fire? characteristicis constituted of a leakyewave g uide,the latter being a .wave guide githat adapted to ipermitelectromagnetic wave l povve gui ded-through I the interior thereof to fescape 'substantially continuously along-its length, as. illustrated: by an unsheathed -dielectric guide I .operatednearcut-ofii In thebest mode of appli- L ca'tionthat I have discovered the antenna is a g.continuously...leaky-r wave, guide consisting. essentially ofta rod of dielectric material having adielectric constant substantially greater. than unity andthaving the characteristic. thatthevelocity off wavepropagation through-the rod, i. e.,- the .pl ia se velocity, is sub stantially. equal to, or'slightly lessthan, the velocity ofnlight in free space.

Av feature of the invention is aivvave-refiector 'or quasi-piston that is adapted.for,-longitudinal movernent withina dielectric rod. njaccorda ce wit another feature of .the in- .vention an antenna.arrayisconstituted of a multiplicity of end-firedielectric rod antennas dis- ,posedside by side.

A The, invention embraces: also azscanning array o fi fi n 'yh d fi ly directed ,end fire: antennas Qrethe 9.;Whicl;1 e fectivelyare cyclically arrayed in groups for each direction of scanning.

37 Claims. t; zsq e easm 2 {Ihe nature ofltne. present, invention :and varius bgfects,v f atl rceeand advantages ini addition hose pointedpu-t above.=vvill appearcmore :tully frona the following description ofzthe .embodi- 5 merits or the invention thatar'e illustrated in the finest In-athadrawings: 1 illustratesamendefireidielectric rod annna ystem in accordance-awith the invention; I, Su- Z and 3, -arecurve;diagramsrelevant t -the 51 atenna i ie 4 illustrates an array of rodiantennas; :tOSBeShQWimodifi'cations ofiiFig. l'e and Rig lpto 1; illustrate radioscanningsystems n aocordancenvith.the. invention.

ef; ring moreso'articularly now to:Fig-.-1; there pwnantenna. system[ comprisingea red I of solid dielectric material that is unsheathed .e thrggugfhoutsthe .;greater; part of? itsolen'gth and a which is fitted -atgoneiend withr meansit'for excitpg 1 with i ultraehighirequenovelectromagnetic ,or fonreceivingsuch waves intericeptediand ransmitted byr-the rode; The :phase velocity of a i enratync omfield .configurationiproparough :a dielectric rod is rdependent on 4 l e y'fixed .by;.the:dielectric constant ofthe material. comprising it and by. its transverse dimensions," ther diameter being; thexsignificant pameter in;-.theicase of.rarrod of '.icircu1a'r cross egtion, as--L'-.haVe; disclosed-heretofore. These tors; can be; ands-ares seiner-related. with -the V U fre(p er-icy;that=theavelocity .of propaga- ,1; .mughathe rodgl .isvsubstantially the-same a th&-tXBlQcity c oft.waveepropagation: in iree iwaoeers mQrepanticularly; substantially thesame as the velocity of propagation.alongethe aod' in rthe spaceiimmediately-surrounding the rod, For a-iparticularudielectric; rod simacie of -spolystyrer 1e.:.haxing;a. dielectric constant? of- 2.5' the u lclationr -betiveen ,d/ ;,..-the d'iameter' of -the--rod 40trm-easured iwaveslengths fandu-thez ratiol'c/vg of gthewelocity of propagation in freetspace tdithG e elQQity ofipropagation'in theirod; takes the form 1;;111ustrated; graphically in'.-Fig'. 2.:e zThe' dominant i or =.Hn;;type of .dielectrically 'guided wave is as- ,;suined. 1;;EIIO1'Ifi-gth9 graph it willbe evident that igtthessignificanti,ratio;approaches ;.asy1nptotica11y a value equal to the square root ofgthe dielectric constant ebfor increasing values of? diameterand vthat: insthemther direction the ratio-approaches '2iasymptotica11y thexdesired value 'of unityas the diameter. is; progressively -.red-uced; Experience .Qshowssthatrfor; the-particular rese -contemplated Figl:2.a good ra'nge' ofoperating diam'eterslies -.,:be t.ween .:0;4 2e:and 50.5 'In this' rangeathe velocity of propagation is somewhat less than but within 7 about ten per cent of the velocity in free space.

flector at the other end and with a traveling detector or the like measure the length of the standing wave appearing along the surface of the guide. In a modification of this method the detector remains fixed and one moves the plane reflector, the latter having an aperture through which the guide extends. If this measured wavelength falls within the range noted above, conditions are appropriate for end-fire radiation.

When it is not essential that the operating frequency be of some predetermined value, it may be adjusted over a range until a frequency is found which the measuring technique described indicates to be productive of the desired velocity of transmission or which yields maximum wave intensity at some distant point on the axis. If a predetermined operating frequency be selected, then it will be necessary either to calculate the phase velocity in terms of the dimensions of the guide or progressively shave or turn down the dielectric rod until measurements indicate that the proper dimensions have been reached. Since the calculations involve troublesome transcendental equations which must be solved graphically it is often more convenient to resort to the experimental procedure. For a cylindrical polystyrene rod about 7.5 wave-lengths long, a diameter of about 0.4% was found to be approximately correct,

Graphical solutions of the equations for different assumed values of the dielectric constant e' are represented in Fig. 3, where the inverse ratio v /c, known as the velocity constant, is plotted against d/A on a somewhat larger scale than that employed in Fig. '2. It will be noted that in the case of polystyrene and other materials having a relatively low dielectric constant there is a comparatively wide range of values of d/x over which the velocity constant is approximately unity, or less than unity by not more than about ten per cent. In other words, the desired velocity ratio and end-fire characteristics tend to be maintained over a comparatively wide range of operating wave-lengths, which in some instances in practice is a characteristic that is more to be desired than higher axial gain over a more limited range of wave-lengths.

Bearing in mind that the operating wavelength may be, for example, of the order of centimeters or less it will be appreciated that the end-fire dielectric rod may be a slender structure especially well adapted for situations requiring a dirigible beam radiator or receiver. A structure of the proportions described could be readily mounted, for example, in an aircraft gun turret for use in object location and radio range finding and for use generally in sighting the gun and directing the aircraft under conditions of poor visibility.

The unsheathed dielectric rod, it will be understood, permits wave energy to escape throughout its length. This is especially true in the lower ranges of the transmission curve shown as Fig. 2. Where, as here prescribed, the internal and external velocities are substantially equal, the wave energy contributed by the dielectric rod to the external field at any point is in such phase as to enhance transmission or radiation in the axial direction. The phenomenon is such, too, that for rods of moderate length the longer the dielectric rod is, the'more sharply is the radiation confined to the axial direction. T0 at least a first approximation doubling the length of the rod in this region doubles the axial gain or sharpness of the radiation pattern.

Added gain may be had, too, by employing a plurality of parallel dielectric rods in array in the manner of the horn arrays disclosed in my application Serial No. 346,175, filed July 18, 1940. Such an array is illustrated in Fig. 4 although only diagrammatically. Details of the individual couplings and of the connections to the common source or receiver are omitted.

To excite the dielectric rod l or to take off the waves intercepted by .it, means of the character illustrated in Fig. 1 may be employed. As shown, a metallic sheath 2 encloses an end portion of the rod and a metallic end cap 3 is,provided. Embedded in the dielectricis a diametral conductor i which in one direction extends through an openin in sheath 2 as the inner conductor of a coaxial conductor tuner-5; In the other direction conductor i extends through the sheath as the inner conductor of a coaxial conductor line 5- which leads to the exciting source I or correspending receiver. The distances from conductor e to end plate 3 and to the other end of sheath 2, respectively, may advantageously be so proportioned in relation to the operating wavelength as to facilitate efiicient transfer of wave power between line 6 and the unsheathed or radiating portion of the rod I. This is a matter of matching impedances and will be considered further hereinafter, To support the rod of clamp B is applied to the sheathed portion of the rod and attached to the top of the supporting column that is mounted on a rotatable base 9; The feed line 6 may be broughtup through the supporting column or even constitute the supporting column, as illustrated.

Fig. 5 shows a modification of the Fig. 1 structure in which the end-firedielectric rod II is of rectangular cross section. The principles underlying the design are those discussed with reference to Fig. 1 and the various parts are proportioned with the same objects in View. In one instance of practice the dielectric rod ll consisted of a bar of polystyrene centimeters long having an e dimension of 2.7 centimeters, an it dimension of 4.7 centimeters, and a measured dielectric constant of 2.5 or 2.6, the e and h dimensions being the cross-sectional dimensions that are respectively parallel and normal to the lines of electric force. The unsheathed portion of the rod was approximately 65 centimeters long and the operating frequency was 3,000 megacycles per second, The operating frequency corresponds to a free space wave-length of 10 centimeters and the indicated wave-length within the rod was approximately the same. The axial gain of the structure relative to a non-directional radiator was found to be about 17 decibels. Where the combination is to be used as a receiver the transverse conductor l4, aligned with the electric field of the waves in the rod and corresponding to conductor 3 of Fig. 1, maybe brought out in one direction through the sheath l2 to a tunable detector E3 of coaxial conductor type and the demodulation products taken therefrom. Good results have been obtained too with a rod of ceramic material having a dielectric constant of about 30.

,Fig. 5 illnstrates 'al so na new .form f piston n guid a;:beatinemscillaturz:21; t1 of;,cl1ambe ,i-fizeateth'ea nd ofi met v .i.rimwerseepickriipcoonductorz3.4,

92211 We ateonfieend ;to;1af-.; coaxiai= tunerwleazds i t; detectoiv.amt-1eXterI-ials:coupling?cirouiw 22:;ar d throu h -that :to receiving; apparatusmot; slimm d. The; -terminal .1 apparatus 1.; illustrated? is necifiqa "Adapted ion. receiving; waves: picke'cl z .ieloet icrrodg; but minor: modifications :tl ifi almiaratusasuitable forjmoduiation smissiomof: waves; Eurther. detailsswill ogndi i 1 ;,e0pending applicatiom serial- I cut- No; 35 64 nowmahandoned,filedOotobemlO; fi frequency termincd;,hygthe Separation of 19% As :slziowmfthewreinforcing:platesltineed the plates and the length thereof, and by proper 15.;fI1QblQ1ififiJE1d-Zil0 thei-freeeend ofsthe -rodg and the proportioning of th e parts,thelsubguidev;cut ofi portiomof it; Within the sheath may he usedias a -a freqi encycan be and th meansdor-iattaching the. radiator and termi-nal-i perating; frequency, th reby., b1o g -w chamber t0$asupportingvzand orienting structure:v transmission. If gthe plates; I5,ua r;e.l at ,1eas Tosprevent-lrefiection 1css=thecoupiiiigeat ti YeiE g hflbn h .cutwffi qtlency of ti; ,2 ;.;fixeirend:-=ef; the -end fire: dielectric-rc d should= subguides may be readily calculated in terms pizovide for: impedance --mat6hiIig-- of the parts: the spacing between plates, I .With closer spac- III-5191189. embodiment illustrated in FE 7"; for ing of the plateszti the length: thereof may be example, theeparts comprise;theunsheathed -rod reduced Without changing the cut-off frequency iivhavingeacertain characteristic"impedance-Zr;- of the snbguides. Althoughgequations are ayail =-25 a metalsh'eathed end seetion-2iihaving-adifierent able in pnblished form vto perrint thes ecessar; characteristic impedance Z2,and---a--holiow- :ham; calculationstqbe tirade itrhayhesaid that t e; her-like guide-portiomzfi into which thetaperedV lower ilimit n ,l hefiliai i between :p l tes i end of therodcxtendsa short distancewThe largely one of.iconvenieirce 77 1 1 The ,die1e chamber-'22E is boHnded at-Qneend by the aper material in the end of the sheathed portlo 1301;:tu redtmaphragrn zewhich-enay;separa;te-it from is slottedto receive.,the-.p1ates ifi andtope t a soume or-receivebtmth left: *Itisa matter" ngit i l:a sfiillfi fi heg of thereioyfe i 1 of=-experience that even'iP-the diaphi agmztbe" bli n readywadiustnient ofthe point otreflectionw V omitted-"a:fairly good--i-mpedancematchmaybe Tl e everal; plates iare mechanicaflyconneot obtained merely bysliding"the dielectric-radium "\athee-chamber' "Milt/i1" the -transmitted, power "is 1 byfil-Plttei m tal c c iothe w s ien is attached ,tojthe assembly The adaptat maximum-.- Fo'r a stiilbetter "match the 1 parts t e structo re toggnides of other than; rectangular}; may -be so proportioned that while theye dimen'e cross-seiition andito"thejreflection of wayertpes siorr'of the sheathedguide 'sectiOn'Z 'is thesame he th nthedeminan type fwi zbe em? 1. as that -of chamber section zs "the -11 dimension; to $1 kil d nk- F i- Q h "=of;1setion2511s v; times 4 that .7 ofwsecfition flv.

met le h t d ve lei e to subdivide it inthe h ine= it n9f th g r ncipies=; nvo ved sugh smgllj:dis qgntinuity as,may, appearsatvthe i ectien o I. if and "lit-m y pensateriv =1b e iustmee. ioiilz eposit on and: apertureefl e i v 1 ,phragm 26." The tapering of theendeofirfthel-rqdc 1 I as; show mak s" he: condition ,iorri oedan e Erper me ev h WI' th i h es se fi v t nt advanta es ar s ur d insac V ange withg another phase: ofthe.presentlinventifilne, hands 1 3 by njakinjg the endefire dielectricerodielasticeor,

long h time;

thelelectric orce} ar d midway et the may ibe constructed rota material such-as. soft ber so thatltheirod,maybe substantiall de-M- fiecte din anydirection atwill. I inasmuch as. the direction ofradiation depends on the orientation of th sunssheatheo jrod portion, Whichismeadily controlled by any suitable'mechanical means,,.itisevidentthat this construction permits rapid radio scanning of any given section ofspace; Inertia r ,v i n ve-e y- 1 I v for it .permits the additi to imme-m Nether-wise, e weak; fer-go hows d-v ntage iiss qn o -eembqciyms als otheefea ures to described." v

33 8- i he ifil fifi ifl Ol 1. 19 'l f l planegderiv ed by gr adually. reducingsthee dimene sst t gecen ems an; .m d m l 1 sionpf-therodtowardlth'e free end thereof..= p teilfl wh p f thecs merw dthesith r i For omev applications flexibilit in pne planefland Whlch 15 disposed parallel t0 and only' may for uchca e a m t-,a1 Wese;=th ,:-Z fec srt e s a th le e e mid-septum 3'0jinay beaddedto the FigJTs'trnc-p of ht fmd hfifil ett iq.ma eria istapered-down F- hire" as shotvn sin Fig., 8. The septnm not only F to P15 2 1 WWW? c n e i f i o lendssupport ar d preyentsiflexingin itsplanebiit it also-may' be used, to control, the elasticity of the s structure and its natural periodofyibration. The is arranged as a wavejguidingcontinuatiomofethe latter feature maybe ofspecial utility ir connec-, rodsi; andlis expanded inqh dimensionitmavo T tionwithobjeotlocators,suchjas.saircraft spotting transmission cut-oft: 'Chamloeimlfieinoludesia-- devi'ces, where it is considered desirablew to scan. trans-yerse,;,metal licfliaphragmeM witha 'centra f the scene "cyclically with a periodicity oitheorder slit jn thelz plane. .'-In the chamber \portiombeof a. -fraot-i 1 1 -of;a'second, for by. properlyj adjiist-l. tw ensiianhragmflfl and theclfised-"left ha'ndendf ing gthe- -e1asticity;;of th'e ,,rod.in .relationlto' the; of chainherewmeans.areeprovided fomintrodueingmass thereoftlie natural period of vibration, of

may be, reduced. and increased. flexibilityyinl one s the flexible rod may be made to coincide more or less with the desired period of scanning. Thus, a dielectric rod of pure gum rubber having a specific gravity of 6.59 and a dielectric constant of 3.5 at 3000 megacycles, having an effective length of 61 centimeters, e and h dimensions of 2.7 and 4.8 centimeters, respectively, and a septum V of brass 0.159 centimeter thick, was found to have a natural frequency of vibration of approximately 100 per minute. On substituting a septum of steel about 0.32 centimeter in thickness the resonant frequency may be increased to about cycles per second. The principle of scanning applied above to a single plane may be extended to two planes by a suitable modification of the antenna structure. For example, one may use as the supporting member a relatively small metal rod of rectangular cross-section surrounded by the necessary dielectric either in circular or rectangular form. By suitably proportioning the dimensions of the core relative to its elastic properties and the mass of the surrounding dielectric, it is possible to give one period of scanning in the vertical plane and another in the horizontal plane at the same time retaining the very desirable radiation characteristics.

' Fig. 9 illustrates a modification of the Fig. 1 structure adaptin it for. oscillatory variation of the angle of fire. The principal changes as compared with Fig. l are the provision of a bayonet joint 32 in the vertical coaxial feed line, thereby permitting angular adjustment of the upper end of the feed line and the transmission elements mounted thereon, and a heavy helical-sprin 33 connecting the stationary and movable parts. The spring is proportioned in relation to the moment of inertia of the movable parts to give the desired periodicity. The necessary power required to maintain the structure in continuous vibration may be applied through an escapement or any of a variety of mechanical devices. It will be appreciated that the coupling between the feed line and the rod, and therefore also the intensity of radiation, is not afiected by the angular movement of the radiator. V

For rapid scanning for higher gain and angular definition than can be achieved with a single rotating beam radiator or receiver it is of'course possible to provide an array of beam antennas] and to rotate the array. This ma lead, how-.

ever, to cumbersome structures of considerable weight and bulk not well adapted for many situations in practice. In accordance with one phase of the present invention the performance.

of an angularly adjustable or rotatable array is achieved with a stationary array of divergent beam antennas and a movable distributor. latter connects the antennas, successively in The groups, to the exciting source or receiver and introduces phase shift of such amount that the divergent antennas constituting the operative group at any instant cooperate to form a; single beam of high intensity. Fig. 10 shows diagrammatically one form which the invention may take.

Referring to Fig. 10, a large number of stationary'end-fire dielectric rods 35 are disposed radially in circular array about a central point, and a distributor or contactor 36 mounted for rotation about the central point is arranged to connect a source 31 (or receiver) to the feed ends of the dielectric rods a group at a time. By way of specific example the array may comprise thirtyends of the connected group of rods are not in the same phase relation but differ in phase by such amount that the'radiation from each rod contributes eflectively to the production of a single sharp beam or, in other words, to the formation of a plane wave front w-a that is normal to the central rod of the group. If the phase tpo of the waves supplied to the central rod be as signed a reference value of zero then the waves supplied to the two rods next adjoining should be advanced in relativephase by an amount 1P1 such that, approximately,

s gn-cos a For practical cases like that cited above (122 is approximately four times o1. It should be understood that the principles involved do not require that the group consist of an odd number'of rods, although this is considered the better arrangement.

One practical embodiment in accordance with the-Fig. l0 diagram is illustrated in Fig. 11. For simplicity only a few of the dielectric rods comprising the complete array are illustrated. The distributor 36 in this case is a hollow pipe guide of rectangular cross-section comprising an arcuate portion 39 that slides along the open ends of coupling chambers 40 associated with the feed ends of the end-fire dielectric rods 35, and radial portions 4| that extend from the extremities of the arcuate portion to the central source 31. The latter comprises a coaxial conductor line which has an end portion 38 integrally connected with the distributor 36 and adapted for rotation therewith about the axis of the line. The outer vertical walls of guide sections 4|, assuming the coaxial line to be vertical,extend through the outer conductor of the coaxial section 38 to tangential contact with the large inner conductor while the other walls terminate at the outer conductor. With this arrangement of parts the coaxial conductor waves supplied through the line to section 38 are translated 7 into horizontally polarized guided waves of dominant type in the guide sections 4|. Moreover, the two guided Waves as thus established are in aiding phase relation in respect to the supply of wave power to the arcuate section 39. For efiicient coupling, coaxial section 38 is extended above the guide portions 4| and capped with a metallic reflector, the length of the extension being critically related to the operating frequency and adjusted for maximum radiation.

The arcuate portion 39 orthe distributor has in its outer vertical face a plurality of apertures, represented as vertical slots 42, one for each of the rods comprising the group, and having the same angular separation. Through the slots 42 wave power is communicated to the coupling six dielectric rods and the distributor may connect live at a time with the source. The distributor is of such nature that the waves. supplied to the feed chambers 40, the open ends of which are otherwise completely closed'by the outer face of the distributor. The chambers 40 may be as illustrated in Figs, 7 and 8 but flared as'shown so that they are contiguous at the outer face of the distributor, so that as the distributor rotates wave powers-continuously se tum-"e 'one'orfanother facilitated a I a It is to be notedthatthe waves supplied through the radial branches f4! reach first the 'outefpair of rods 35 and that the phase hereis "advanced relative to the phase at the central rod liv n v en eer' e dme th t me: of v transmission from the outermostslots lz to the central slot. 1 Similarly there is a phase advan'ce at the i'nrierpair of slots relative to the central slot. 'If'necessary, phasing loops 43 may be interppsed between slots in the arcuategui deportion 39 whereby the electrical distance and phase displacement between slots can be adjusted as desired. suitableproportioning of the parts these phase differences may be made to coincide with the desired values of 1 and 2 hereinbefore indicated. a

Another embodiment in-accordance with Fig.

lO isiIIustrated in Fig. 12. Onlythe distributor andsource are shown, for the coupling chambers and dielectric rods may be the same as in Fig, 11. In this case the vertical feed guide consists of a cylindrical metal pipe guide with a rotatable end portion 44 terminated by an end reflector. Waves of; symmetric magnetic or H01 type are supplied through the guide to a plurality of longitudinal slots EE'spaced apart circumferentially in the wall ofrguide section 44. Integrally, connected to section 44 are five contiguous flaring'pipe guides 46 of rectangular cross-section which aredisposed over respective slots;45iand-supplied with wave power therethrough. At their other ends. the guides 46 are covered by an arcuate metal plate adapted to ride against the exposed endsof the coupling chambers 49, and vertical slots 42 are provided as before for escape of wave power into the coupling chambers from the respectively associatedguides 45; The required relative phase displacements 61 and 2 are-obtained-by phase shifters 47 disposed in the two outer pairs of'ra dial guides. The phase shifters may be 'ofany suitable type, such asa pair of iris diaphragms or other reactors critically spaced apart in relation to the operating wave-length and the phase i tde r whatis'claimed is: i 1. Arr antenna system comprising as the wave radiating or intercepting element a rodof di' electric material having a dielectric constant substantially greater than unity, and-means at one end of said rod for launching into -said rod or; for receiving therefrom only electromagnetic waves of a predetermined operating frequency;

space continuously along said'g uide or forreceiving from said guide; such waves propagated therethrough and excited therein by radio Waves incident thereon. t

4. In a microwave radio system, a radio antenna comprising a continuously leaky electromagnetic wave guide, said guide being terminated at one end in free space, a conductively. shielded non-radiating transmission line coupled tothe other end of said guide in substantially-impedance, matching relation therewith, and wave translating means including said line for exciting' in said guide electromagnetic waves of a predetermined frequency and field configuration for guided propagation therethrough toward, said one end withradiation of wave energy continuously along said guide, or for receivingv from said guide such waves propagated therethrough toward said other end and excited therein by radio waves incidentthereon.

, 5. A microwave radio system comprising a leaky wave guide as a Wave radiating or radio wave intercepting element thereof, said. guide having a free end terminatingin space, and'wave translating means coupled to saidguide at a-distance from said free end for applying ultra-.high frequency electromagnetic waves to said guide for propagation therethrough toward said free endwith continual radiation therefrom Or for receiving from said guide such" waves e'X"c'ited therein by radio waves intercepted by saidguide, said translating means being itself non-radiating, and saidguide being transversely dimensioned to guide the travel of the waves being propagated in said guide with a phase velocity substantially equal to that of light in free'space.

6 A microwave radio system comprising as a wave radiating orintercepting element thereof a leaky ave guide the transmission cut-off he quency of which substantially coincides with the operating wave frequency, said guide being terminated at one end'in free space, and, wave ex; citing or receiving means coupled to said guide at a point a plurality of wavelengths removed from said one end for exciting withinjsaid guide the wave'sto be radiated or for receiving there from waves excited therewithin by incident radio Waves '7. A microwave radiofsy'stehi c6 the antenna a continuour'sly l'eti y,,W v d' which'is dimensioned to have ata'll'op'erating Wave frequencies a velocity constant, that is less than but within about 10 per cent of unitygand wave translating means at one end onlyof said guide for exciting said guide with the waves to be radiated or for receiving radio waves intercepted by said guide, said translating meaiisbethe transmission cut-off frequency of said rod being not substantially greater than the: said operating frequen-cy, the length of said rod being at least several wave-length at the operating frequency.

. 2:; As a radio antenna, a leaky wave guide having a transmission cut-01f frequency that substantially coincides with the operating wave frequency.

3. A microwave radio system comprising: as 'a" waveradiating or radio wave interceptingelement' thereof a continuously leaky wave guide,- and non-radiatmg wave translating means LCOUP' pledto said guide for exciting therein-electromagnetic waves of apredetermined" frequency adapted for guided propagation therethrough with leakage of wave energy therefrom into free ing configured for selective translation of non circularly symmetric guided Waves in said guide; and sai system being further characterized by an end fire radiation pattern. I a e a 8; An antenna for ultra-high frequency radio waves comprising an unsheathed dielectric rod havinga dielectric constant substantially greater than unity, said rod being so dimensioned that the velocity of wave propagation theiethrough at the operating wave frequency is approximately equal to the velocity of electromagnetic waves in free space." I I l 9. A microwave radio system comprising an elongated, slender antenna "having an end-fire characteristic, said antenna consistingof a leaky wave guide, and guided wave exciting or receiving means coupled to said guide at only one point thereof for exciting Waves in said guide for radi excited therein by incident radio waves.

10. As a radio antenna, a leaky wave guide comprising an unsheathed rod of dielectric material having a dielectric constant substantially greater than unity, said guide having a transmissi on cut-off frequency that is at least approximately the same as the frequency of the waves being radiated or received.

11. In a microwave radio system, an antenna comprising a continuously leaky wave guide, said guide being transversely dimensioned to have a phase constant substantially equal to that of free space over a predetermined wave frequency range, and wave translating means for operating said antenna only at frequencies within said frequency range.

12. As a radio antenna, a rod of low-loss dielectric material having a dielectric constant of about two and one-half at the operating wave frequency, said rod being of substantially circular cross-section and having a diameter of from four-tenths to one-half wave-length at the operating wave frequency.

13. As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod being of circular cross-section and having a diameter such that its phase constant is substantially unity at the operating wave frequency.

14. As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod having transverse dimensions such that the transmission cut-off frequency of said rod is substantially equal to the operating wave frequency.

15..As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod being of circular cross-section and ha ing a diameter such that the transmission cutoif frequency of said rod is substantially equal to the operating wave frequency.

16. As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod being transversely dimensioned to guide the travel of waves there through with a phase velocity that is substantially equal to that of light in free space at the operating wave frequency.

17. A microwave radio system in which the antenna comprises a rod of dielectric material having a dielectric constant substantially greater than unity, means for exciting electromagnetic waves of predetermined frequency and of dominant type in said rod for propagation therethrough and radiation laterally therefrom or for receiving such waves intercepted by said rod and propagated therethrough, said rod being transversely dimensioned to guide the said waves propagated through said rod with a phase velocity so closely approximating that of light in free space that said rod exhibits an end-fire directional characteristic with respect to the said waves. 7

18. A microwave radio system comprising as a Waveradiating or intercepting element thereof a rod of dielectric material having a dielectric constant substantially greater than unity, and electromagnetic wave translating means coupled to said rod for launching waves into said rod for propagation therethrough with substantial escape of wave energy laterally therefrom into space, or for receiving from said rod Waves propagated therethrough and excited therein. by

intercepted radio waves.

19. A microwave radio system comprising as a wave radiatingor intercepting element thereof a rod of dielectric material having a dielectric constant substantially greater than unity, the length of said rod being at least several wavelengths at the operating wave frequency, and electromagnetic wave translating means coupled to one end only of said rod, said translating means constituting means for launching waves into said rod for propagation therethrough with substantial radiation of wave energy laterally therefrom into space, or for receiving from said rod waves propagated therethrough and excited therein by intercepted radio waves.

20. In a microwave radio system, an antenna comprising a rod of dielectric material having a dielectric constant that is at least double that of'air, an ultra-high frequency wave transceiver, and means coupling said transceiver to said rod adjacent one end thereof for exciting waves in said rod for propagation therethrough toward the other end thereof with continual radiation therefrom or for" receiving waves propagated in theopposite direction through said rod and excited therein by intercepted radio waves, and means for preventing substantial translation of wave energy between said transceiver and space excepting as said translation takes place through said rod, said other end of said rod terminating in space.

21. A combination in accordance with claim 20 in which saidlast-mentioned means comprises means conductively shielding said coupling means to provide a substantially non-radiating connection between said rod and said transceiver.

22. As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod being transversely dimensioned to guide electromagnetic waves of the operating wave frequency through the interior of saidrod with a phase velocity that is, throughout the length of said rod, less than but within about ten per cent of the velocity of light in free space.

23. As a radio antenna, a rod of dielectric material having a dielectric constant substantially greater than unity, said rod being transversely dimensioned to guide electromagnetic waves of the operating wave frequency through the interior of said rod with a phase velocity that is substantially equal to that of light in free space.

24. In a microwave radio system, an antenna comprising an unsheathed rod of dielectric material, and means for establishing in said rod or receiving therefrom dielectrically guided waves of dominant type, said rod being dimensioned to guide said waves through the interior of said rod with a phase velocity that is substantially equal to the phase velocity of electromagnetic Waves in space externally of the rod, whereby said rod has an end-fire characteristic.

25. A system in accordance with claim 18 in which said rod is of substantially rectangular cross-section.

26. A system in accordance with claim 18 in which said rod is tapered.

27. An antenna array comprising a multiplicity of unit antennas in accordance with claim 9 disposed side by side.

28. An antenna array comprising a multiplicity of like directed unit antennas in accordance with claim 1.

29. A radio antenna in accordance with claim 2 comprising an elastically flexible leaky wave guide, and means for flexing said guide.

30. A structure in accordance with claim 18, said rod of dielectric material having the electrical and mechanical properties of gum rubber. a

31. A structure in accordance with claim 18 including a strengthening member extending length-wise through the rod.

32. A structure in accordance with claim 18, said leaky wave guide comprising a flexible rodof dielectric material and a stiffening member extending lengthwise of the rod. 2

33. A structure in accordance with claim 18 including a metallic stiffening member contiguous with said material and extending along the: length of said rod, said rod and stiffener being so proportioned that the velocity ofpropagationl of waves transmitted therethrough is at least approximately equal to the velocity of said waves in free space.

34. A structure in accordance with claim 33 in I which said stiffener is a flat strip embedded within the said dielectric rod and disposed with its plane normal to the electric vector of said waves.

35. A-- dielectric rod for the transmission of microwaves, coupling means for exciting said rod or receiving waves therefrom, said rod being conductively sheathed for a portion of its length comparable with the length of said waves, said coupling means being embedded wholly within said sheathed portion and positioned therein for maximum coupling with the unsheathed portion of said rod.

36. A microwave radio antenna system com prising a rod of a dielectric material that has a dielectric constant substantially greater than that of air, said rod having a conductively unsheathedportion that is a plurality of wavelengths long at the operating wave frequency and a conductively sheathed portion contiguous to said unsheathed portion, said sheathed and unsheathed portions difiering in characteristic impedance, said sheathed portion having a refiecting termination at the end thereof remote from said unsheathed portion, and wave translating means coupled to said sheathed portion at a point spaced from said remote end for exciting-waves to be propagated in andradiated from said unsheathed portion or for receiving waves intercepted by and propagated in said unsheathed portion. 2

37. A system in accordance with claim 36 in which the length of said sheathed portion and the spacing of said coupling point from the said remote end are correlated for maximum coupling between said translating means and said unsheathed portion of said rod. 1

GEORGE C. SOUTHWORTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 1 Name 1 Date 2,129,711 Southworth Sept. 13, 1938 2,188,649 Carter Jan. 30, 1940 2,202,380 Hollmann May 28, 1940 2,206,923 Southvvorth July 9, 1940 2,223,224 Newhouse Nov. 26, 1940 2,304,540 Cassen Dec. 8, 1942 

